1. Field of the Invention
The present invention relates to a rolling bearing and a rolling bearing assembly used, for example, for supporting a machine tool main shaft or the like.
2. Description of Related Art
For a rolling bearing, there is a technique in which an oil supply hole is provided in an outer ring so as to communicate between an outer diameter portion and an inner diameter portion and an oil is supplied through the oil supply hole (Patent Document 1). For example, a rolling bearing used for supporting a machine tool main shaft or the like is rotated at a high speed in an air-oil lubrication system with use of the above technique.
[Prior Art Document]
[Patent Document 1] JP Laid-open Utility Model Publication No. 63-180726
FIG. 15 shows a frequency distribution result of a bearing with an inner diameter of φ100 mm at 13000 min−1. When a bearing having an outer ring provided with an oil supply hole is mounted on a main shaft or the like and rotated at a high speed in the air-oil lubrication system, there may be a problem that the noise level becomes very high depending on a flow volume of supplied air or the diameter of the oil supply hole. This noise is wind noise which is generated when air jetted from the oil supply hole collides against rolling elements then rotating at high speed, and is harsh high-frequency sound. This frequency coincides with the rolling elements passing frequency relative to the outer ring. If it is possible to reduce the level of the high-frequency noise, work can be conducted without being much bothered by the noise, even during a high speed rotation of the main shaft. That is, this leads to improvement of the working environment.